The mission of the San Francisco Adolescents and Sexually Transmitted Diseases Cooperative Research Center (SFCRC) is to identify the unique risks associated with Sexually Transmitted Diseases (STDs) among adolescents through the conduct of high quality, interdisciplinary research and to foster a productive scientific environment for STD researchers. We will examine the target population most affected by STDs in the San Francisco Bay Area: African American adolescents living in urban neighborhoods. Our interdisciplinary focus includes an emphasis on adolescent development and the acquisition of infection, including risk factors, immunologic correlates of viral STD pathogens, and the diffusion of infection through networks of sexual partners. Our specific goals are to: 1. Characterize disease transmission and spread at the population level by characterizing a sexual network that determines disease spread, including identification of individual behaviors that predict risk (Project 1: STD Risks Associated with Adolescents' Sexual Networks). The dissemination of gonorrhea and chlamydia, as well as participation in risky behaviors, will be assessed. 2. Identify immunologic factors associated with initial human papillomavirus (HPV) infection and identify host factors predictive of persistence of infection and subsequent development of squamous metaplasia (Project 2: Immunologic Correlates of Initial HPV infection). 3. Identify immunologic factors associated with herpes simplex virus infections (HPV), types 1 and 2, including the role of factors including: acquisition, manifestation, and natural history progression of disease (Project 3: Epidemiology & Immunobiology of HSV infection). Two cores serve these projects: The Biostatistics Core oversees all data management and analyses. The Cohort Core provides logistical support for recruitment, screening, consent, enrollment, and retention of study subjects for center projects.